Most of the work in this project has been devoted to developing reliable reagents to measure IgE with specificity to the antigens used in this project. In addition, some efforts have been made to develop hybridomas producing IgE with specificity to a desired antigen. Specific antisera for the reliable detection of IgE have been obtained, but hybridomas producing IgE have not been yet developed. Presently, enrichment techniques to concentrate the numbers of IgE-producing cells before fusing with tumor cells are under investigation. Employing the IC challenge to detect immunity to experimental pertussis in mice, it has been shown that vaccines made from Bordetella pertussis containing pertussigen (Pertussis toxin (Ptx)) stimulate the production of antibodies of the IgE isotype with specificity to surface antigens of B. pertussis. Strains that do not produce Ptx do not stimulate IgE antibodies. Antisera containing IgE antibodies to surface antigens protected mice from IC challenge, while those without it did not protect mice. These experiments are under further study to settle whether the IgE antibodies are indeed important in the protection of mice to IC challenge.